I'm not running it to play optimally; I'm running it because it's fun :P I do take sorcery secondary on Viktor.
If you can burst hard in the first few hits of combat, then there is potentially an argument to be made that First Strike is stronger, since it amplifies all damage you deal by 10%, which is what makes me think it's pretty good on TF especially as the game gets later. But I haven't mathed it out so maybe it's not as strong as comet or ignite from spellbook? TF usually runs inspiration anyway, so it's not like he is taking comet